Intensity modulation in telecommunications applications is often achieved with electro-absorption modulators (EAMs), which offer small size and low power and can be operated at high speed. EAMs generally operate based on the Franz-Keldysh effect, that is, a change in the absorption spectrum of a semiconductor via a change in the bandgap energy as caused by an applied electric field. Integrated EAMs are usually structured as vertical diode mesas with an electrical contact on the top for one polarity and electrical contacts on one or both sides of the mesa for the other polarity; having electrical contacts on both sides reduces the series resistance of the device, which is important for high-speed modulators. In many implementations, the intrinsic-type layer of the diode mesa includes a quantum well structure to exploit the quantum-confined Stark effect for high extinction ratios.
Band-edge effects such as the Franz-Keldysh effect and the quantum-confined Stark effect have a strong temperature and wavelength dependence. Therefore, it is generally desirable to keep the operating temperature of devices using these effects, such as EAMs, within a narrower range than the ambient temperature. In various photonic circuit designs, such temperature stabilization is achieved with a local heater placed in the vicinity of the diode mesa. In some photonics fabrication platforms, however, is not possible to have both a heater and an electrical contact running along the same side of a diode mesa, rendering it difficult to both minimize series resistance and locally regulate the operating temperature of the device. A device designer may, thus, have to choose between a fast device and a thermally regulated device.